Metal fiber yarn, fabric comprising metal fiber yarn, method for manufacturing fabric, and use of fabric

ABSTRACT

Disclosed is a metal fiber yarn, which is used to produce a membrane for a surface combustion burner having a wide combustion range and high porosity, a fabric produced using the metal fiber yarn, a method for manufacturing the fabric, and the membrane for the surface combustion burner using the fabric. Having a length of 0.45-0.6 m/g and a torsion ratio of 1-9 turns/m, the metal fiber yarn comprises 50-100 unidirectionally oriented metal fibers, which are produced by combing randomly oriented metal fibers manufactured by a melt extraction method. The membrane has uniform combustion efficiency, a wide combustion range, and high porosity.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a metal fiber yarn, a fabric comprisingthe metal fiber yarn, a method for manufacturing the fabric, and amembrane for a surface combustion burner using the fabric. Moreparticularly, the present invention pertains to a metal fiber yarn,which can be used for manufacturing a membrane for a surface combustionburner having a wide combustion range and high porosity, a fabriccomprising the metal fiber yarn, a method for manufacturing the fabric,and the use of the fabric as a membrane for the surface combustionburner.

2. Description of the Prior Art

Generally, a surface combustion burner is produced using a porous metalfiber membrane (media), and mixture gas of fuel and air is combusted onthe surface of the porous metal fiber membrane. The membrane for thesurface combustion burner is heated at a high temperature of 1000° C. ormore, thus it is produced using a heat-resistant metal or ceramic fiber.

With respect to a conventional technology, which relates to a metalfiber used for a porous gas burner membrane and to the membrane producedusing the metal fiber, PCT/EP01/04197 discloses a method of producing agas burner membrane using yarns comprising metal fibers, and a fabriccomprising the yarns. The machined metal fiber bundle is surrounded bypolymers or natural fibers, and is consolidated with each other using abinding agent. After the fabric is produced using the metal fiber yarn,the binding agent and the polymers or the natural fibers are removedfrom the fabric. The method of producing the yarns by surrounding themetal fibers using the binding agent and the polymers or the naturalfibers as disclosed in the above PCT patent is frequently employed toproduce a yarn using metal fibers produced through a machining process.As known in the art, the metal fibers, which are mechanically processedusing devices shown in FIGS. 3 to 4, have a predetermined orientationafter the machining is finished, and are a bundle of the metal fibershaving a desired diameter due to a fine drafting process.

PCT/EP02/05062 discloses a burner membrane produced using a fabric whichcontains at least 60 wt % of machined metal fiber bundle having a bundlevoluminousity in the range of 1-15% and a torsion ratio of 10-80turns/m.

Furthermore, PCT/EP96/03107 discloses a fabric and a membrane for a gasburner produced using the fabric. In the patent, metal filaments, whichare produced through a machining process such as U.S. Pat. No. 4,930,199and have an equivalent filament diameter of 15-150 μm, are parallellycombined with each other without a twisting operation using a bindingagent to form bundles of filaments, and the bundles of filaments arewoven or knitted to produce the fabric.

However, the above PCT patent is problematic in that, since metalfibers, which are produced through a machining process according to U.S.Pat. Nos. 4,930,199 and 5,071,713, are unidirectionally oriented and thebundle of metal fibers includes the predetermined number of metalfibers, it is difficult to produce a porous membrane for a combustionburner when lengths of the fibers are short or fiber distribution isunparallel or nonuniform.

SUMMARY OF THE INVENTION

Therefore, the present inventors have conducted extensive studies intoproduction of a metal fiber yarn having a unidirectional orientationfrom metal fibers, which have a nonuniform distribution or are randomlyoriented, thereby accomplishing the present invention.

An object of the present invention is to provide a metal fiber yarnhaving a unidirectional orientation, which is used as a membrane for asurface combustion burner having high porosity and a wide combustionrange, and is produced using randomly oriented metal fibers manufacturedby a melt extraction method.

Another object of the present invention is to provide a fabric producedusing the metal fiber yarn.

A further object of the present invention is to provide a method formanufacturing the fabric using the metal fiber yarn.

Yet another object of the present invention is to provide the membranefor the surface combustion burner having uniform combustion efficiencyand high porosity.

According to an aspect of the present invention, there is provided ametal fiber yarn having a length of 0.45-0.6 m/g and a torsion ratio of1-9 turns/m. The metal fiber yarn comprises 50-100 unidirectionallyoriented metal fibers, which are prepared by combing randomly orientedmetal fibers as shown in FIG. 1(a), manufactured by an apparatus used ina melt extraction method as shown in FIG. 2.

According to another aspect of the present invention, there is provideda fabric produced using the metal fiber yarn.

According to a further aspect of the present invention, there isprovided a method for manufacturing the fabric. The method comprisescombing randomly oriented metal fibers, which are produced through amelt extraction method, to prepare unidirectionally oriented metalfibers; producing a metal fiber yarn, which consists of 50-100unidirectionally oriented metal fibers and which has a length of0.45-0.6 m/g and a torsion ratio of 1-9 turns/m; and producing thefabric using the metal fiber yarn.

According to still another aspect of the present invention, there isprovided a surface combustion burner membrane having high porosity andhigh combustion efficiency, which is produced using the fabric.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 a is a picture showing randomly oriented metal fibers producedthrough a melt extraction method, FIG. 1 b is a SEM (Scanning ElectronMicroscope) picture (200 × magnification) showing transverse sections ofthe metal fibers produced through the melt extraction method, and FIG. 1c is a SEM picture (600× magnification) showing the longitudinal surfaceof one metal fiber produced through the melt extraction method;

FIG. 2 schematically illustrates an apparatus used in the meltextraction method;

FIG. 3 schematically illustrates a device used in a cutting methodbelonging to a conventional machining process;

FIGS. 4 a to 4 c schematically illustrates a drawing method belonging tothe conventional machining process;

FIG. 5 is a SEM picture (500× magnification) showing longitudinalsurfaces of metal fibers produced through the conventional machiningmethod;

FIG. 6 is a SEM picture (50× magnification) showing transverse sectionsof metal fibers produced through the conventional cutting method;

FIG. 7 is a SEM picture (1000× magnification) showing transversesections of metal fibers produced through the conventional drawingmethod;

FIG. 8 illustrates a metal fiber yarn according to the presentinvention;

FIG. 9 is a picture of a fabric produced by weaving the metal fiberyarns according to the present invention;

FIGS. 10 a and 10 b illustrate lower and upper sides, respectively, of afabric in which slit-type flame holes are formed, according to thepresent invention;

FIG. 11 is a picture of a fabric produced by knitting metal fiber yarnsaccording to the present invention;

FIG. 12 illustrates pictures of flames having a calorific value of 418KW/m² during combustion using a membrane for a combustion burneraccording to the present invention; and

FIG. 13 illustrates pictures of flames having a calorific value of 1063KW/m² during combustion using the membrane for the combustion burneraccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a detailed description will be given of the presentinvention.

A metal fiber yarn according to the present invention comprises metalfibers which are produced through a melt extraction method and have acrescent section, a diameter of 20-70 μm and a length of 10-20 cm. Whenthe diameter is less than 20 μm, undesirably, the fibers are easilybroken while they are combed. When the diameter is more than 70 μm, itis impossible to desirably produce the yarn because the number of thefibers constituting the yarn is small. When the length of the fiber isless than 10 cm, undesirably, it is difficult to produce the yarnbecause of the short length. It is difficult to produce a metal fiberthat is longer than 20 cm and the diameter is 20-70 μm, through the meltextraction method.

In the melt extraction method as described in U.S. Pat. No. 6,604,570,which has been made by the applicant of the present invention, acylindrical rod having a diameter of 12 mm is provided at an inductioncoil as a melting unit and is melted at an end thereof using anapparatus of FIG. 2 according to the present invention. The moltenportion of the rod comes into contact with a disk, which rotates at ahigh speed of 1-100 m/sec, to instantaneously produce metal fibershaving a diameter of 20-70 μm. The metal fibers each have a crescentsection as shown in FIG. 1 b, and a plurality of protrusions whichprotrude by a height of 1-5 μm from a longitudinal surface thereof asshown in FIG. 1 c. Each metal fiber, which is produced through the meltextraction method, has protrusions having heights of micron units, thusfalling-out of the metal fiber is prevented in the course of producingthe yarn. Accordingly, it is possible to easily produce the yarn usingthe metal fibers of the present invention in comparison with metalfibers produced through a conventional machining process.

Typically, a cutting method and a drawing method are employed to producea fine metal fiber through the machining process. In the cutting method,a metal sheet is wound like a coil as shown in FIG. 3, and a section ofthe wound metal sheet is cut to produce metal fibers. In the drawingmethod, after a plurality of surface-treated wires is firstly drawn, thefirstly drawn wires are collected in a protection pipe 1 as shown inFIG. 4 a, and secondly drawn as shown in FIG. 4 b. The drawing isrepeated a predetermined number of times, and the protection pipe ismelted to produce metal fibers as shown in FIG. 4 c. However, thesemachining processes are different from the melt extraction method inthat metal is repeatedly mechanically processed at a temperature that islower than a melting point thereof to produce the fine fiber and eachmetal fiber manufactured by the machining process has a smooth surfacewithout the protrusions as shown in FIG. 5.

Improved Fecralloy, which contains an iron-chromium-aluminum-based alloyas a main component, and 0.05-0.5 wt %, preferably 0.1-0.3 wt %, Zr isused to produce the metal fibers of the present invention. When afabric, which includes Fecralloy containing Zr in the above amount, isused as a membrane, an oxidation life is excellent. Typical Fecralloy isused in the present invention, and it comprises, for example, 70-83 wt %iron (Fe), 18-27 wt % chromium (Cr), 3-7 wt % aluminum (Al), and0.05-0.5 wt % zirconium (Zr).

The metal fiber yarn according to the present invention is producedusing randomly oriented metal fibers which are produced using Fecralloythrough the melt extraction method.

The fine metal fibers produced through the melt extraction method arerandomly distributed with each other as shown in FIG. 1 a, and it isnecessary to orient the fibers to produce the yarn. The randomlyoriented metal fibers may be continuously combed many times in order toarrange the metal fibers parallel to one another. The orientation isrepeated until the one yarn consists of about 50-100 metal fibers. Whenthe number of fibers is less than 50, they become tangled because thenumber of fibers constituting the one yarn is small, thus it isdifficult to desirably produce the yarn. When the number of fibers ismore than 100, breathability is reduced and an intensity change range isnarrow during combustion, thus gas is undesirably discharged. Withrespect to this, the metal fiber has a diameter of 20-70 μm and a lengthof 10-20 cm.

Furthermore, the yarn is produced so as to have a length of 0.45-0.6 m/g(0.45-0.6 Nm) and a torsion ratio of 1-9 turns/m. If the length per gramis less than 0.45, the yarn is thick, and thus, undesirably, porosity isreduced. If the length per gram is more than 0.6, the yarn is thin, thusit is difficult to maintain the thickness of the yarn.

Additionally, when the yarn is used as a membrane for a burner, the yarnhas a predetermined torsion ratio so that the metal fibers are notfallen out from the yarn while a gas fuel is easily discharged betweenthe metal fibers. In other words, if the torsion ratio is more than 9turns/m, the metal fibers are densely arranged in the metal fiber yarndue to a characteristic of the metal fibers produced through the meltextraction method, thus it is difficult to conduct the discharge of thefuel gas. If the torsion ratio is less than 1 turn/m, the metal fibersare easily fallen out from the yarn, thus it is difficult to desirablyproduce the yarn.

The metal fiber yarn of the present invention is produced by means of atwisting operation and has the torsion ratio of 1-9 turns/m. Hence, themetal fibers are not removed from the yarn and the shape of the yarn ismaintained, thus it is easy to produce a fabric using the yarn.Furthermore, in order to reinforce the maintenance of the shape of theyarn, the yarn can further comprise polymer or natural fibers, which aredisposed in nearly parallel arrangement in the yarn. The polymer fibersmay be polyamide fibers, polyester fibers, polyethylene fibers,polypropylene fibers, acrylic fibers and polyvinylalcohol polymers, etc.and natural fibers may be cotton or wool. The weight of polymer ornatural fibers in the yarn is less than 15% by weight of the yarn,preferably even less than 10% by weight. The polymer or natural fiberscan be removed easily by burning or any other appropriate means.

As well, since fuel gas is easily discharged between the fibers, it ispossible to produce the fabric for a surface combustion burner membranehaving high porosity and excellent combustion efficiency.

The yarn, in which the metal fibers produced through the melt extractionmethod are combed, is processed to form a fabric having a density of1.0-4.0 kg/m², and the fabric thus formed is used as the membrane forthe porous surface combustion burner.

If the density of the fabric is less than 1.0 kg/m², since the fabric,in which the yarns having a predetermined thickness are arranged at awide interval, is produced, discharge of fuel gas is large, thuscombustion is insufficiently achieved. If the density is more than 4.0kg/m², since the interval between the yarns is too narrow, discharge offuel gas is low, and thus, undesirably, combustion is scarcely achieved.The fabric produced so as to have a density of 1.0-4.0 kg/m² is 0.5-2.5mm thick.

Since the fibers produced through the melt extraction method of thepresent invention are oriented unidirectiionally and twisted to producethe yarn, the fibers are not fallen out from the yarn, thus the shape ofthe yarn is stably maintained. Furthermore, the fabric is produced sothat the interval between the yarns is constant, and it is possible touse the fabric as the membrane for the burner having excellentcombustion efficiency, combustion range, and porosity.

It should be understood that the term “fabric” used in the presentinvention is intended to include any fabric produced by weaving orknitting the yarns of the present invention.

Furthermore, according to the present invention, in the fabric, weft andwarp are arranged perpendicular to each other, and flame holes, whicheach have two parallel warps and two parallel wefts as sides thereof,are formed on both sides of the fabric.

The flame holes correspond to sparing recesses on the lower and uppersides of the fabric. The flame holes are formed in the shape of a slitin which a ratio of length to width is 10:1 or less, and preferably,1:1-10:1. If the ratio of length to width is more than 10, since theflame holes must be formed using 3-4 lower yarns, undesirably, thefabric is slack. If the slit, in which the ratio of length to width is10:1 or less, has desirable porosity, it is possible for the fabricincluding the slit to have any ratio of length to width.

When the fabric of the present invention is used as the membrane for thesurface combustion burner, fuel flows through the slit-type flame holes,which are formed by the yarn of the lower side of the membrane, andthrough fine pores of the fabric into the upper side of the membrane,and combusted at the slit-type flame holes of the upper side.Accordingly, mixture gas is further uniformly distributed. In otherwords, fuel gas, which is fed to the lower side of the membrane, isdivided by the yarns of the lower side of the membrane, and flowsthrough the slit-type flame holes, the fine pores of the fabric, andfine pores between the metal fibers constituting the yarn to the yarn ofthe upper side of the membrane. At this time, gas spouts through thepores of the membrane and the yarn and through the slit-type flame holesof the upper side of the membrane, and is combusted, thus fuel isuniformly discharged and combusted.

Particularly, since fuel gas spouts little by little through the poresformed between the metal fibers, the flow rate of gas between the metalfibers increases even though a small amount of fuel is fed, thus thecombustion is stably achieved. In other words, the fine pores betweenthe fibers act as fine slit-type flame holes, thus a wide combustioncharacteristic ranging from a high intensity region to a low intensityregion is realized. When the density of the fabric is 1.0-4.0 kg/m²,porosity is 70-95%.

Hereinafter, a detailed description will be given of the presentinvention, with reference to the accompanying drawings.

Used as a raw material in the present invention, the metal fiber isproduced through the melt extraction method using Fecralloy containingFe, Cr, Al, and Zr components, and randomly oriented as shown in FIG. 1a. A diameter and a length of the fiber are 20-70 μm and 10-20 cm,respectively, and a section and a longitudinal surface of the metalfiber are shown in FIGS. 1 b and 1 c, respectively. The metal fiberproduced through the melt extraction method has a crescent section asshown in the picture of FIG. 1 b, and the longitudinal surface, on whicha plurality of protrusions are formed in a height of 1-5 μm, as shown inthe picture of FIG. 1 c.

Meanwhile, longitudinal surfaces of metal fibers, which are producedthrough a machining process, are shown in FIG. 5. The longitudinalsurfaces of the metal fibers produced through the machining process aresmooth without protrusions as shown in the picture of FIG. 5. Transversesections of metal fibers, which are produced through a cutting methodbelonging to the machining process, are shown in FIG. 6. Additionally,during the production of metal fibers through a drawing method, atransverse section of a protection pipe 1 including a plurality of metalfibers of FIG. 4 b is shown in FIG. 7. In other words, as shown in FIG.7, when the metal fibers are produced through the drawing method, themetal fibers are surrounded by a plurality of protection pipes, which isshown in the form of dark boundary lines at the center of FIG. 7.

In the metal fibers produced through the melt extraction method of thepresent invention, removal of the metal fibers from the metal fiber yarnis prevented due to a plurality of protrusions formed on surfaces of themetal fibers as shown in a picture of FIG. 1 c, thus it is possible toeasily produce the yarn without using a separate binding agent and/orsurrounding or enveloped polymer.

FIG. 8 illustrates the metal fiber yarn according to the presentinvention. In order to produce the metal fiber yarn of the presentinvention, the metal fibers 2 are continuously combed many times to beunidirectionally oriented, and 50-100 plies of metal fibers 2 are formedinto one ply of yarn, thereby preparing the metal fiber yarn. The metalfiber yarn has a length of 0.45-0.6 m/g and a torsion ratio of 1-9turns/m: In the metal fiber yarn (FIG. 8) of the present inventionhaving the above torsion ratio range, the metal fibers 2 are not fallenout from the yarn and the shape of the yarn is maintained, thus theproduction of the fabric is easy. When the fabric thus produced is usedas a membrane for a combustion burner, the flow rate of gas in fine gapsbetween the metal fibers 2 increases even though a small amount of fuelis supplied, thus gas easily sprouts from the yarn and stable combustionis achieved.

The metal fiber yarn of FIG. 8 is woven or knitted to produce thefabric, and the fabric thus produced is used as the porous membrane forthe surface combustion burner. Particularly, a picture of a fabric,which is produced through a weaving process according to the presentinvention, is shown in FIG. 9, lower and upper sides of the woven fabric(membrane) are shown in FIGS. 10 a and 10 b, respectively, and a pictureof a fabric, which is produced through a knitting process, is shown inFIG. 11. Lower and upper sides of the fabric have the same shape. Forconvenience of understanding, however, the side of the fabric thatdirectly comes into contact with fuel gas is considered as the lowerside (FIG. 10 a), and the opposite side of the fabric is considered asthe upper side (FIG. 10 b).

As shown in FIGS. 10 a and 10 b, the fabric of the present invention,which is produced through the weaving process, is produced by weavingthe metal fiber yarns as warp 3 and weft 3′ so that the warp and theweft are arranged perpendicular to each other. Furthermore, the wovenfabric has a density of 1.0-4.0 kg/m² and a thickness of 0.5-2.5 mm.

During the weaving process, flame holes (A, A′), which each have twoparallel warps and the two parallel wefts as sides thereof, are formedin the shape of a slit in which a ratio of length to width is 10:1 orless.

A better understanding of the present invention may be obtained throughthe following examples and a comparative example which are set forth toillustrate, but are not to be construed as the limit of the presentinvention.

EXAMPLE 1

A cylindrical rod having a diameter of 12 mm was provided at aninduction coil as a melting unit, heated to 1600° C., and was melted atan end thereof using an apparatus of FIG. 2 according to the method ofU.S. Pat. No. 6,604,570. The molten portion of the rod came into contactwith a disk, which rotated at a high circumferential speed of 20 m/sec,to instantaneously produce metal fibers having a diameter of 50 μm. Themetal fibers were randomly arranged, and each had a crescent section anda length of about 10-18 cm. Components of each metal fiber were 22 wt %chromium, 5.5 wt % aluminum, 0.3 wt % zirconium, and the balance of iron(Fe).

The randomly distributed metal fibers were continuously combed 100 timesto be unidirectionally oriented to produce a metal fiber yarn consistingof 80 plies of metal fibers. The yarn thus produced had a length of 0.55m/g and a torsion ratio of about 8 turns/m.

EXAMPLE 2

The yarn, which was produced using the metal fibers produced through themelt extraction method as Example 1, was woven to produce a fabrichaving a density of 1.5 kg/m² and a thickness of 1.5 mm as shown in FIG.9. As shown in FIGS. 10 a and 10 b, flame holes were formed on bothsides of the fabric in the shape of a slit in which a ratio of length towidth was 5:1. Furthermore, the fabric included 14 yarns per inch (5.5yarns/cm), which each consisted of 80 plies of metal fibers, andporosity of the fabric was 85%.

Mixture gas, in which fuel gas was mixed with air in a variable mixingratio of the following λ, was fed into the fabric, and combustion wasconducted. When the combustion was carried out so that the ratio of airto fuel gas (λ: air/fuel gas) was 1.05, 1.25, and 1.42, a calorificvalue was 418 kW/m². Furthermore, when combustion was implemented sothat the ratio of air to fuel gas (λ) was 1.03, 1.22, 1.41, and 1.69,the calorific value was 1,063 kW/m². Pictures of flames, which changedaccording to changes in the ratio of air to fuel gas during combustion,are shown in FIGS. 12 and 13. When the fabric of the present inventionwas used as a membrane for a surface combustion burner, a widecombustion intensity range, at which the ratio of minimum combustionintensity to maximum combustion intensity was 1:2.5, was assured, and itwas possible to realize both radiation and transition modes.

For example, when the combustion membrane of the present invention wassubjected to combustion characteristic analysis, the calorific value of200-2,000 kW/m² was assured using burners of 20,000 and 50,000 kcal/h.Therefore, it was possible to produce a combustion membrane having thewide combustion intensity range, in which the ratio of minimum calorificvalue to maximum calorific value was 1:10. A heat capacity (kcal/h) andan intensity capacity (kW/m²) of the burner were easily controlled usingparts constituting the burner.

COMPARATIVE EXAMPLE 1

Metal fibers were produced through a cutting method disclosed in U.S.Pat. No. 4,930,199. A metal sheet, which consisted of 22 wt % chromium,5.5 wt % aluminum, 0.3 wt % zirconium, and the balance of iron (Fe), andhad a thickness of 0.1 mm, was wound around a rotatable shaft like acylinder as shown in FIG. 3. The metal sheet was cut using a cutter,which moved at a speed of 0.10 mm/min and had a width of 20 mm, at acutting speed of 72 m/min so that a face angle (γ) between the cutterand the shaft was 32 degree, thereby creating the metal fibers, whicheach had a rectangular shape having a length of 50 μm and a width of 20μm. However, the metal fibers, which were produced through the cuttingmethod disclosed in the above U.S. Pat. No. 4,930,199, included fibershaving a length of 20 cm or more, and longitudinal surfaces of thefibers were smooth. Accordingly, it was impossible to produce yarnhaving a low torsion ratio according to the present invention.

When the metal fibers produced through the melt extraction method wereused to produce the yarn, the metal fibers were not fallen out from theyarn due to the plurality of protrusions formed on the longitudinalsurfaces of the metal fibers. On the other hand, when using the metalfibers produced through a machining process, the metal fibers wereeasily fallen out from the yarn because the surfaces of the fibers weresmooth, thus the shape of the yarn was not maintained.

Since a plurality of protrusions are formed on surfaces of randomlyoriented metal fibers, which are produced through a melt extractionmethod, falling out of the metal fibers from a metal fiber yarn isprevented, thus it is possible to easily produce the yarn. Furthermore,the yarns produced according to the present invention may be woven orknitted to produce a fabric. Particularly, when the yarn is used as amembrane for a burner, fuel uniformly flows from a lower side of themembrane to an upper side of the membrane due to pores formed on lowerand upper sides of the fabric, and fine pores between the metal fiberyarns having unidirectional orientation and a predetermined torsionratio. Accordingly, it is possible to produce a combustion membranehaving a wide combustion range in which the ratio of the minimumcalorific value to the maximum calorific value is 1:10. Additionally,the membrane of the present invention has excellent combustionefficiency and porosity.

1. A metal fiber yarn comprising 50-100 unidirectionally oriented metalfibers, wherein said unidirectionally oriented metal fibers are preparedby combing randomly oriented metal fibers manufactured by a meltextraction method, and said metal fiber yarn having a length of 0.45-0.6m/g and a torsion ratio of 1-9 turns/m.
 2. The metal fiber yarn as setforth in claim 1, wherein each of the metal fibers has a crescentsection, a length of 10-20 cm and a protrusion that protrudes by aheight of 1-5 μm from a surface thereof.
 3. The metal fiber yarn as setforth in claim 1, wherein the metal fibers are made of aniron-chromium-aluminum-based alloy containing 0.05-0.5 wt % zirconium.4. The metal fiber yarn as set forth in claim 3, wherein the metalfibers are made of an iron-chromium-aluminum-based alloy containing0.1-0.3 wt % zirconium.
 5. The metal fiber yarn as set forth in claim 3,wherein the metal fibers are made of an iron-chromium-aluminum-basedalloy containing 70-83 wt % iron, 18-27 wt % chromium, 3-7 wt %aluminum, and 0.05-0.5 wt % zirconium.
 6. The metal fiber yarn as setforth in claim 1, wherein a cylindrical rod having a diameter of 12 mmis provided at an induction coil of a melting unit and melted at an endthereof, and a molten portion of the cylindrical rod comes into contactwith a disk, which rotates at a high speed of 1-100 m/sec, toinstantaneously produce the metal fibers having a crescent section inthe melt extraction method.
 7. The metal fiber yarn as set forth inclaim 1, wherein the metal fiber yarn further comprises polymer ornatural fibers, which are disposed in nearly parallel arrangement in theyarn.
 8. A fabric comprising the metal fiber yarn according to claim 1.9. The fabric as set forth in claim 8, wherein the fabric has a densityof 1.0-4.0 kg/m².
 10. The fabric as set forth in claim 8, wherein thefabric is a woven fabric or a knitted fabric.
 11. The fabric as setforth in claim 8, wherein the fabric has porosity of 75-95%.
 12. Thefabric as set forth in claim 8, wherein flame holes are formed in a slitshape, a ratio of length to width of which is 10:1 or less, on lower andupper sides of the fabric.
 13. A method for manufacturing a fabric,comprising: combing randomly oriented metal fibers, which are producedthrough a melt extraction method, to prepare unidirectionally orientedmetal fibers; producing a metal fiber yarn, which consists of 50-100unidirectionally oriented metal fibers and which has a length of0.45-0.6 m/g and a torsion ratio of 1-9 turns/m, by means of a twistingoperation; and producing the fabric using the metal fiber yarn.
 14. Themethod as set forth in claim 13, wherein each of the metal fibers has acrescent section, a length of 10-20 cm and a protrusion that protrudesby a height of 1-5 μm from a surface thereof.
 15. The method as setforth in claim 13, wherein the metal fibers are made of aniron-chromium-aluminum-based alloy containing 0.05-0.5 wt % zirconium.16. The method as set forth in claim 13, wherein a cylindrical rodhaving a diameter of 12 mm is provided at an induction coil as a meltingunit and melted at an end thereof, and a molten portion of thecylindrical rod comes into contact with a disk, which rotates at a highspeed of 1-100 m/sec, to instantaneously produce the metal fibers havinga crescent section in the melt extraction method.
 17. The method as setforth in claim 13, wherein the metal fiber yarn further comprisespolymer or natural fibers, which are disposed in nearly parallelarrangement in the yarn.
 18. The method as set forth in claim 13,wherein the fabric is a woven fabric or a knitted fabric.
 19. A membranefor a surface combustion burner using the fabric according to claim 8.20. The membrane as set forth in claim 19, wherein the fabric has adensity of 1.0-4.0 kg/m².
 21. The membrane as set forth in claim 19,wherein the fabric is a woven fabric or a knitted fabric.
 22. Themembrane as set forth in claim 19, wherein the fabric has porosity of75-95 %.
 23. The membrane as set forth in claim 19, wherein flame holesof the fabric are formed in a slit shape, a ratio of length to width ofwhich is 10:1 or less, on lower and upper sides of the fabric.